The present invention relates to shrink-fit tools and, more particularly, to shrink-fit tools with mechanical retention members.
Conventional toolholding arrangements involve mechanical chucks and the like for holding shanks of rotating tools such as milling, drilling, and boring tools, and for holding shanks or other portions of turning tools. In some circumstances, an alternative to a mechanical chuck is desired. It is also known to secure tools relative to toolholders by a shrink-fit technique whereby the toolholder is heated so that a tool-receiving opening in the toolholder expands sufficiently to receive a part, such as a shank, of the tool. When the toolholder cools, the opening in the toolholder contracts and the tool is secured in the opening by an interference fit. JP 2002-355727 discloses a shrink fit tool with a pin engaging groove 10 and a flat surface member 9 at 90° to the pin engaging groove 10. A 90° corner is disposed between the pin engaging groove 10 and the flat surface member 9.
An aspect of the present invention addresses a problem with shrink-fit tools in which the tool tends to creep outwardly relative to the toolholder. For example, in shrink-fit tools using tools with positive axial angles, such as solid end milling cutters, due to pulling and twisting forces on the tool, the tool moves outwardly relative to the toolholder. This can adversely affect the accuracy of a machining operation performed with the shrink-fit tool.
It is desirable to provide a shrink-fit tool that can reduce problems associated with tool creep in shrink-fit tools.
According to an aspect of the present invention, a shrink-fit tool comprises a tool and a toolholder, one of the tool and the toolholder having a male shank portion and the other one of the tool and the toolholder having a body portion including female opening for receiving the shank portion, the female opening being adapted to change in size upon heating the body portion to receive the shank portion and upon cooling of the body portion to clamp the shank portion by an interference fit, the shrink-fit tool comprising a pin adapted to extend into the female opening in a direction lateral to an axis of the female opening for mechanically retaining the shank portion in the female opening, the shank portion comprising a lateral recess extending laterally to an axis of the shank portion, the shank portion comprising an axially extending recess, an end of the axially extending recess being disposed at an end of the shank portion, and the lateral recess being disposed remote from the end of the shank portion and connected to and at least partially circumferentially offset from the axially extending recess, wherein the shrink-fit tool is part of a rotating tool arranged for cutting a workpiece when rotated in a first direction about the axis of the shank portion, a recessed, curved transition region of constant depth being provided between the lateral recess and the axially extending recess, the lateral recess and the axially extending recess being of sufficient depth such that rotation of the shrink-fit tool in the first direction during a cutting operation tends to urge the pin into the lateral recess so that the shank portion is mechanically retained in the female opening and, when the shank portion is rotated relative to the female opening of the body portion in a second direction opposite to the first direction, the pin is adapted to be received in the axially extending recess so that the shank portion is adapted to be withdrawn from the female opening of the body portion.
According to another aspect of the present invention, a method of mounting a tool to a toolholder comprises heating a body portion including female opening for receiving a shank portion so that the female opening changes in size to permit insertion of the shank portion, the shank portion comprising an axially extending recess, an end of the axially extending recess being disposed at an end of the shank portion, and a lateral recess disposed remote from the end of the shank portion and at least partially circumferentially offset from the axially extending recess and connected to the axially extending recess by a recessed, curved transition region of constant depth; cooling the body portion to clamp the shank portion in the female opening by an interference fit; restraining axial movement of the shank portion relative to the body portion with a pin disposed in the lateral recess in the shank portion and in an opening in the body portion; rotating the shank portion relative to the female opening of the body portion, with the pin in the opening in the body portion, so that the pin moves from a position in which the pin aligns with the axially extending recess to a position in which the pin aligns with the lateral recess and axial movement of the shank portion is thereby restrained; and rotating the shank portion relative to the female opening of the body portion, with the pin in the opening in the body portion, so that the pin moves from the position in which the pin aligns with the lateral recess to the position in which the pin aligns with the axially extending recess and withdrawing the shank portion from the female opening of the body portion.
According to yet another aspect of the present invention, a tool for a shrink-fit tool assembly is disclosed and comprises a tool having a male shank portion adapted to be received in a female opening of a toolholder, the female opening being adapted to change in size upon heating the body portion to receive the shank portion and upon cooling of the body portion to clamp the shank portion by an interference fit, the tool comprising a recess for receiving part of a pin disposed between the shank portion and the body portion for mechanically retaining the shank portion in the female opening, the shank portion comprises a lateral recess extending laterally to an axis of the shank portion, the pin being adapted to extend into the lateral recess, and the shank portion comprises an axially extending recess, an end of the axially extending recess being disposed at an end of the shank portion, and the lateral recess being disposed remote from the end of the shank portion and at least partially circumferentially offset from the axially extending recess and connected to the axially extending recess by a recessed, curved transition region of constant depth.